Field of the Invention
The invention relates to a process for electrochemically (galvanically) applying a surface coating. In particular, the invention relates to a process for depositing a surface coating on a component as described in my earlier U.S. Pat. No. 5,415,761.
Surface structures described therein are obtained by chemical etching after coating or by mechanical machining such as grinding or sand-blasting. A hard-chromium layer is then applied to the thus created surface structure. The various processing steps required in the production of such components are elaborate and they require complex process technology. The final cost is essentially determined by the mechanical or chemical processing steps necessary for generating the structure.
In structuring metal coating layers, use is also made of elaborate and very difficult-to-control dispersion-deposition processes in which a specific surface structure is obtained through organic or inorganic foreign substances which are included, for example, in a chromium layer and/or which block the growth of the chromium layer during the deposition process. The result is a rough surface. The foreign substances are present in the form of dispergate in the electrolyte.
U.S. Pat. Nos. 4,468,293 and 4,515,671 to Polan et al. relate to a process for electrochemical coating in which a pulse-like current is used for nucleation. A first portion of the pulse has a relatively high current for less than 0.1 sec. and the second portion of the pulse has a much lower current. If a suitable current density is used, the resulting nuclei form a dendritic structure. It is thus possible in one working operation to generate rough dendritically structure surfaces. The current density is understood to be the mean current density at the cathode surface.